VB is the market leader in above-ground geothermal installations to sustainably heat greenhouses

Go directly to:

• What is geothermal energy?
• How does geothermal energy work?
• How much energy does geothermal provide?
• Types of geothermal energy
• Sustainability
• Advantages and disadvantages
• Earthquakes
• Involved parties
• State of the technology
• Expected developments

What is geothermal energy?

Geothermal energy involves using energy from the earth to heat greenhouses, buildings, and homes. Hot water lies deep within the earth. Geothermal energy involves pumping this water to the surface and converting it into energy. This sustainable process is known as geothermal energy.

How does geothermal energy work? 

Geothermal energy starts from a depth of 500 meters. Hot water is present in sand and rock layers at that depth. By drilling into the ground, hot water can be pumped to the surface and converted into energy. This geothermal energy is also known as geothermal heat.

The deeper the geothermal wells, the hotter the water. The Earth's surface temperature is about 10°C, and the water gets approximately 3°C warmer per 100 meters. For instance, water at a depth of 1 kilometre is about 40°C, and at 2 kilometres, it's 70°C. In the Netherlands, multiple geothermal projects involve drilling to depths of 2 or even 3 kilometres. At these depths, the water's temperature ranges from 70 to 100°C. Geothermal energy extracted from depths of 4 kilometres or more is referred to as Ultra-Deep Geothermal (UDG), but no UDG projects are currently underway in the Netherlands.

Pumping up the hot water is a large-scale project requiring collaboration among specialized companies. VB specializes in above-ground geothermal heat installations, and our installations are located at various sites in the Netherlands. Explore our geothermal projects to see what we have accomplished.

To utilize geothermal heat, a receiving station, also known as a heat unit, is required in the respective building.

Doublet

To pump up the hot water, two wells are drilled deep into the earth: a production well and an injection well. These wells together form a doublet and serve a crucial function. The production well brings up the hot water. After pumping up the hot water, it remains within a closed circuit. Heat exchangers then transfer the heat from this circuit to water flowing through the heat network. A distribution station then transports this heated water to greenhouses, homes, and other buildings. The cooled water is returned to the geothermal installation, where the injection well pumps it back into the ground.

The tops of the production well and the injection well are located near the geothermal installation, just a few meters apart above ground. However, underground, their ends are spaced 1.5 to 2 kilometres apart. This is done to prevent the cooled water being pumped back into the ground from rapidly cooling the hot water source (reservoir).

Did you know…
There are also geothermal installations with three wells. These are called triplets.

VB: Market leader in geothermal energy 

VB has over half a century of experience in heating, designing, and constructing heat networks for the industry and greenhouse horticulture. We are at the forefront of the latest applications and technologies, and we carefully execute the entire project for you. With the use of waste heat and geothermal energy, we strive for maximum sustainability.

VB is a market leader in designing and implementing the entire above-ground installation for geothermal energy utilization. VB has installed 80% of the existing geothermal sources in the Netherlands. Want to know more? Read all about our geothermal solutions.

How much energy does geothermal energy provide?

Geothermal projects provide energy for approximately 4,000 to 10,000 homes. The actual number depends on the depth of the geothermal wells and the capacity of the heat source. Deeper wells produce hotter water and more energy. The permeability of the subsurface also influences the energy output. Before starting each geothermal project, a precise estimation is made of the recoverable energy, but the actual capacity is certain only after the well has been drilled.

Baseload

Geothermal energy is particularly suitable as a baseload for a heat network, meaning the minimum amount of heat needed for most of the year. This allows the heat source to run continuously and provide consistent heat. Geothermal sources are often designed for this baseload, which helps to keep costs manageable. However, multiple heat sources are needed to ensure continuous heat supply to consumers.

Backup installation

Every geothermal installation has a backup system. This backup installation is used in situations where the standard system cannot deliver, such as during maintenance or cold periods when the demand for geothermal heat increases. This demand might be met by a gas boiler, biomass boiler, heat storage, or waste heat source. This is also known as peak load. The combination of heat sources is essential for the sustainability of the heat network. The quantity and types of sources depend on peak demand, buffer capacity, and infrastructure.

Types of geothermal energy

There are different types of geothermal energy, and within these types, there are many variations. The types of geothermal energy are determined based on the depth of the wells.

Ground energy

Ground energy involves wells drilled to depths of up to 300 meters. Ground energy is what is referred to when discussing heating homes with a heat pump.

With this form of geothermal energy, groundwater is extracted from the ground and stored. The temperature of this water is a maximum of 20°C and can be heated to 55°C using a heat pump. This heat pump can be individually connected to a house or building, provided it is well insulated.

Geothermal energy

Geothermal energy is present when hot water is extracted from the ground at a depth of at least 500 meters. The resulting energy is called geothermal heat and is a heat solution for collective use with a single extraction installation (30m²). Most geothermal projects in the Netherlands reach depths of 2 to 3 kilometres. Geothermal energy is widely used in Dutch horticulture.

Ultra-deep geothermal energy

Ultra-deep geothermal energy (UDG) refers to wells drilled from depths of 4 kilometres or more. Currently, there are no UDG projects in the Netherlands, but they may be developed in the future. UDG projects can extract even more heat from the ground, enabling even larger projects to be heated.

Sustainability

Geothermal energy is a sustainable method of heat extraction and is the future for heating greenhouses (and homes). Greenhouse heating is still largely reliant on gas, but the use of geothermal heat for greenhouse heating is increasing. Geothermal heat is a renewable heat source, meaning that the underground heat being pumped up is naturally replenished. Additionally, geothermal heat is CO2-free, making it a crucial element in the sustainability of the Dutch energy landscape. However, electricity is needed to pump the water, so heat pumps are often installed with solar panels in the Netherlands.

Cooling

In a geothermal installation, the ground will have cooled down after several decades (30 to 40 years). In response to this, heat from the surroundings will flow into the earth. However, this doesn't happen only after 30 years; it occurs immediately after extracting the first heat. The cooling of the ground due to heat extraction happens faster than allowing the cooled ground to naturally warm up again. Therefore, after 30 to 40 years, production might be stopped if the temperature of the produced water becomes too low. It's possible to drill a new injection well from the same geothermal installation, with the endpoint placed farther away. The cooled area then has time to warm up again. The speed at which this happens depends on various conditions, but it can certainly take several decades.

Is geothermal completely gas-free?

Geothermal is not completely gas-free. It's possible that natural gas may come up along with the pumped water from the ground. Fortunately, this gas can be captured and used, for example, in a gas boiler. Another option is to pump the gas back down the injection well along with the return water. Additionally, for every geothermal project, a backup boiler is always installed. Depending on the energy source, this backup boiler might emit CO2.

The pros and cons

Geothermal energy is a new way of heat extraction and is gaining recognition due to its sustainability benefits. What are the pros and cons of geothermal energy?

Advantages of geothermal energy

Advantage 1: Sustainable

Netherlands aims to have a sustainable energy supply by 2050. To mitigate climate change, CO2 emissions must be reduced. Geothermal energy hardly leads to CO2 or other emissions. Geothermal energy is a clean alternative to natural gas, with a significant advantage: the ratio between the delivered heat energy and the energy required to extract that heat. In technical terms, this is referred to as the COP (Coefficient of Performance) of geothermal energy. The COP is much higher than that of a heat pump, making geothermal energy a logical and sustainable choice for existing, less well-insulated homes.

Advantage 2: Local energy

Geothermal energy is available in many regions. By extracting heat locally, we become less dependent on market prices of fossil fuels and international markets and influences. Moreover, geothermal energy has indirect positive impacts on the rest of the world. As geothermal energy can relieve the electricity grid, fewer materials are needed from the rest of the world. This means less production and transportation of these materials, resulting in less harm to people and the environment.

Advantage 3: Reliable energy source

Geothermal energy has been used in various places around the world for decades. The technology is not dependent on weather, wind, or seasonal influences, making it a reliable energy source. Another advantage is that geothermal heating uses materials with a relatively short supply chain. In the Netherlands, geothermal energy has secured a robust share in the sustainable energy mix for greenhouse horticulture. Therefore, geothermal energy is a proven technology in the Dutch energy transition. Safety for humans and the environment is ensured in various ways, with a clear distribution of responsibilities among companies, permit providers, and regulators.

Advantage 4: Large scale

Geothermal energy is one of the cheaper alternative energy sources to natural gas. Currently, geothermal energy still requires subsidies. Cost reductions and economies of scale offer an attractive future perspective, as a geothermal doublet is suitable for large-scale applications. In greenhouse horticulture, it often involves heating an entire greenhouse complex. Geothermal energy provides a logical and efficient heat source for a large neighbourhood or multiple neighbourhoods within a municipality. Several doublets located together in the same location can provide heat for more than 50,000 homes and do this by claiming relatively little space above ground. Several doublets cover an area of about half a football field.

Disadvantages of geothermal energy

Disadvantage 1: High installation costs

The costs of installing a geothermal system are high. Many different parties are involved in a geothermal project, and material costs are extremely high. This means that setting up a geothermal installation requires a significant investment.

Disadvantage 2: Risks of groundwater contamination

There are risks of groundwater contamination due to geothermal drilling. This can impact drinking water. The following are the associated risks:

Risk 1: Waste heat

Residual heat is present around the injection well. This residual heat can warm up the surrounding soil, which can also warm up the groundwater. However, this groundwater must never be warmer than 25 degrees Celsius if we intend to use it as drinking water. For this reason, injection wells are not allowed to be drilled in drinking water areas.

Risk 2: Drilling issues

It's possible that insufficient sealing of separating layers can result in drilling through groundwater packages. Another possibility is that drilling mud with potentially contaminated substances can infiltrate groundwater packages or a so-called aquifer, which is a water-bearing layer.

Risk 2: Oil and gas wells

Old oil and gas wells near a geothermal injection well can pose a higher risk of contaminating groundwater. This is because old wells may be compromised or not properly sealed. As a result, formation water from the geothermal installation's reservoir can come up through an old well and enter the groundwater.

Disadvantage 3: Risk of earthquakes

There is a small risk of earthquakes due to geothermal activities. This is related to the seismic risk associated with pumping water back into the ground through the injection well. More about geothermal energy and earthquakes:

Geothermal energy and earthquakes

Pumping groundwater up and down keeps volume differences in the reservoir generally small, resulting in little to no subsidence. However, geothermal energy, or geothermal heat extraction, does pose a small risk of earthquakes. This seismic risk mostly occurs in geothermal installations where the injection well (which pumps water back into the ground) is located near underground active faults. If the injection well is not near active faults but rather in well-permeable layers, then there is a low seismic risk (risk of earthquakes).

When a geothermal installation is planned to be drilled near active fault zones, authorities are required to conduct more research. This oversight is carried out by the State Supervision of Mines (SodM), which advises the Minister of Economic Affairs and Climate on risk assessment. The Minister of Economic Affairs and Climate then grants the permit for geothermal energy extraction at that location and monitors the relevant geothermal companies to ensure they adhere to all agreements.

Involved parties

A geothermal project is an extensive undertaking involving multiple parties. Let us provide you with more information.

Building owner

This can be the owner of a house (private individual) or even a greenhouse for horticulture (commercial).

Geothermal source and district heating system operator

This can be a heat supplier (existing or new) or the municipality in collaboration with this party.

The municipality

Municipalities also play a significant role in geothermal projects. The municipality is involved in identifying parties that can take up the exploitation of a source or district heating system.

Permit issuer

Ministry of Economic Affairs and Climate. Naturally, a geothermal project cannot commence without a permit. Geothermal energy, also known as geothermal heat, falls under the Mining Act. To obtain a permit for this, it must be granted by the Minister of Economic Affairs and Climate.

Network operator

Network operators are also among the parties involved in geothermal heat extraction. For electricity network operators, there are hardly any changes. However, for gas network operators, gradual phasing out is planned for the future.

State of the technology

Currently, there are approximately 25 geothermal sources in the Netherlands. These are primarily used for heating greenhouses, such as the Aardwarmte Maasdijk project, in which VB plays a significant role. In addition to geothermal energy's application in horticulture, there are initiatives in the Netherlands to connect buildings to district heating systems, or even projects focused solely on the built environment. In the Netherlands, we are still in the early stages of these endeavours, but abroad, there are already more projects aimed at the built environment. For example, in Paris, there have been doublet projects heating the built environment for decades. Or in Munich, where geothermal heat extraction for the built environment began a decade ago.

There are still many areas for which it is unknown whether they are suitable for geothermal heat extraction. To make these so-called "white spots" transparent, the government has initiated the SCAN project: Seismic Campaign Geothermal Netherlands. This project is carried out by Energie Beheer Nederland (EBN).

Expected development

Geothermal energy is a young method for achieving sustainable heat extraction, so there are still plenty of ongoing developments. Currently, the most significant developments are:

• Ultra-deep geothermal energy: There is currently a lot of research being conducted on UDG.
• Low-temperature geothermal energy (LTA): Research is also being conducted on extracting geothermal energy with shallower drilling. The advantage is that these drills can be completed more quickly and at a lower investment cost. However, the temperature is lower, so the water needs to be further heated (upgraded) using a heat pump, which also consumes energy.
• Regulations and legislation: Developments are ongoing in the field of regulations and legislation related to geothermal energy. Currently, there is an amendment to the Mining Act and the Heat Act. This amendment allows Energie Beheer Nederland (EBN) to participate as a partner in geothermal projects. This change makes a wealth of knowledge available, as EBN, as a state enterprise, has always been active in the oil and gas sector in the Netherlands. Additionally, the feasibility of projects can be improved through this legislative change.